1. Field of the Invention
The present invention relates to a scanning probe microscope exemplified by an atomic force microscope (AFM), and more particularly relates to a scanning probe microscope for superimposing a pseudo reference tracing a sample shape reference on an observation image and displaying the result.
2. Description of Related Art
With a scanning probe microscope such as an AFM, in order to detect microscopic texture and structure of a sample surface using mutual interaction between the sample surface and a probe, a cantilever having a probe tip mounted on the distal end of the cantilever is used as a probe. If this type of cantilever is used, an attractive force or a repulsive force is generated based on atomic force between the sample surface and the probe tip when the probe tip is scanned relative to the sample surface. Accordingly, this atomic force is detected as a strain of the cantilever, and if a sample stage is caused to move slowly in the Z axis direction so that this strain is kept constant, that is, so that a gap between the sample surface and the probe tip is kept constant, a slow motion signal at that time or a detected amount of strain represents the shape of the sample surface.
A scanning probe microscope having the above described structure is sometimes used as an inspection device for evaluating whether or not the shape of a sample satisfies specified standards or specifications. As shown in FIG. 18, in the case of confirming whether or not the shape of pits formed on the surface of a CD or DVD satisfies specifications, an application for evaluation is started and four reference cursors L1-L4 are displayed, as shown in FIG. 19. Next, if each of the reference cursors L1-L4 is moved so that an inclined section of a pit is enclosed, an angle θ of the inclined surface is automatically calculated. An operator then refers to a specification document or step-by-step procedure to confirm upper and lower limits θmin, θmax of the inclination angle, and if the angle θ has the relationship θmin<θ<θmax with respect to the upper and lower limits θmin, θmax, it is recognized that the pit has a regular shape.
However, with the above described related art technique, not only is it necessary to position the four reference cursors L1-L4 accurately on respectively separate lines, it is also necessary to confirm whether or not the angle obtained falls within a reference range, which means that the time required for evaluation is prolonged. There is also a possibility of erroneously determining that a sample that is out of spec is within spec (or vice versa) due to an incorrect reading of the specification document.